NComm was my favorite, I used it for years before the internet. According to the text on Aminet, it's possible to run the last version (3.06) on OS1.3 with only 512K, IF, run in 2 colors. Another option would be to find older and smaller versions (older than version 3.0x) of NComm. I switched to NComm because it correctly handled IBM ansi characters, IIRC.
Before NComm I used ACCESS!, I didn't see it on Aminet.
I also liked a program called VLT (I think). It was written by a guy who worked at the Stanford accelerator (I think,

, I also didn't see it on Aminet. EDIT: this could be it
http://aminet.net/comm/term/VLTj5867.lhaIf you don't find something, I could look thru my floppy vault and see if one of these is still readable.
This brings up an interesting question: What happened to all the old stuff from Fred Fish and Elysian that doesn't seem to be on Aminet?